In mobile terminals of a mobile communication system, there are a mobile terminal in an active mode which is communicating (e.g. which has established connection) with a base station, and a mobile terminal in an idle mode which is waiting for communication (e.g. which does not establish connection) with the base station. The mobile terminal in the active mode and the mobile terminal in the active mode measure reception quality concerning serving cells of the mobile terminals and neighboring cells. The mobile terminal in the active mode performs handover based on the measured reception quality, the mobile terminal in the idle mode performs cell selection based on the measured reception quality, and they move between the cells.
With respect to the mobile terminal in the active mode, there is known a technique relevant to moving a mobile terminal to a suitable cell according to a load state of each cell (e.g. International Publication Pamphlet No. WO 2007/060808). With respect to the mobile terminal in the idle mode, there is also known a technique relevant to moving a mobile terminal to a suitable cell according to a load state of each cell (e.g. Japanese Laid-open Patent Publication No. 2008-172373, and Japanese National Publication of International Patent Application No. 2008-523711).